The concept of a redundant array of independent disks (RAID) in a storage array is based on the notion that if data is spread along multiple disks, and one of those disks fails, then the data in that disk can be recovered. There are different types of RAIDs. RAID 5 is based on the loss of a single disk drive. For example, if there are five disk drives, and four data stripes, and one RAID stripe, and any one of those five disks fail, then the data from the failed disk can be recovered from the other four. This would only require an XOR function, and does not have a multiplier.
However, in using RAID 6, there is an ability to recover two failed disk drives. For example, if there are six disk drives with the data spread among four disk drives, and one was the XOR drive, and another drive was the multiplier drive, then out of that group of six drives, one or two drives can be recovered. That's why a multiplier is required for this functionality. This is also sometimes called erasure coding.